Typically, a zone control system includes two or more zones in a building and each zone includes a thermostat for control of the temperature in the individual zone. The zone control systems can be warm air heated, hydronic or hot water heated, or cooled by an air conditioning type of system. While many different types of heating and cooling apparatus can be used, the most common includes a furnace and/or cooling coil to temper air that in turn is circulated by a fan in duct work. The duct work has dampers to control the flow of the air to the individual zones. While many different types of systems can be used, and are contemplated within the present invention, the present discussion will use the terminology of a hot air system in which heated air is circulated. This will simplify the description.
Typically when a multizone system is operated, the thermostats call for heat and a fan circulates the heated air to the zone which initiated the call for heat. The zone normally will have a damper that is driven to an open position. When the zone that is calling for heat is satisfied, the furnace would be turned off and the damper driven to a closed position. This typically leaves a substantial amount of residual heat at the furnace and much of this heat is lost up the stack while the furnace is waiting for the next call for heat.
Another type of loss in this type of a system is a random operation of the dampers for the individual zones without regard to the prior operation of any of the other zones in the system. This random operation is undesirable and tends to be an energy wasting type of operation. Prior art arrangements have recognized the desirability of synchronizing the operation of various zone dampers, but the loss of heat that remains at the furnace when the systems are turned off still has been ignored.